In many medical procedures, it is necessary that fluids to be administered to a patient be heated. For example, whole blood and packed cells are stored in refrigerators at a temperature of approximately 4° C. These fluids often are required to be administered to a patient within a short period of time, which necessitates warming them to a temperature approximately equal to that of the patient, i.e. 37° C.
Great care must be exercised when heating fluids such as whole blood or packed cells to avoid damaging the cells. For example, it is generally accepted that whole blood and packed cells should not be exposed to a temperature above 44° C. This places a severe restriction on the techniques used to heat quickly fluids which have been stored in a refrigerator and which must be administered to a patient within a short period of time.
U.S. Pat. Nos. 3,614,385 (Horstmann), 3,629,552 (Edging), 4,476,867 (Parks), and 4,532,414 (Shah et al.) teach systems for heating blood prior to being administered to a patient. The Horstmann, Edging, and Parks devices use various heat exchangers whereby blood flows through a tube which communicates with a warming fluid in a heat exchanger. It is quite difficult to maintain sterility of the heating apparatus in these systems after the first use because of the complexity of the heat exchangers. The Shah et al. device is simply a heated plate having a groove therein for receiving a tube leading from the bag containing the fluid to be administered.
U.S. Pat. No. 2,910,981 (Wilson et at.) shows a device for conducting blood transfusions. A heat exchanger is in fluid communication with a heating element, and the blood to be ministered passes through the heat ex. changer before being administered to the patient. The heat exchanger comprises a central tube surrounded by an outer tube, and the heating fluid passes through the space between the inner and outer tubes. The heat ex. changer is threadedly connected to valves at opposite ends. No structure is described for supporting the various elements described in the patent.